Field of the Invention
The invention lies in the printing technology field. More specifically, the invention pertains to an apparatus for adjusting an air flow that varies the sheet transport in a printing machine. Furthermore, the invention also relates to a method for adjusting a sheet-feed influencing air flow in a printing machine.
Apparatuses and methods that can be performed with them of the type addressed here are known in the art (see German patent DE 197 42 827 C2). In the prior art systems, the adjustment of an air flow (for instance a forced air flow) that varies the sheet transport is effected by manual adjustment or automated adjustment of valves, embodied for instance as ball cocks, for instance by changing a so-called cock operating angle in a ball cock in such a way that the prevailing air pressure at the particular consumer of the printing machine, such as a sheet guide baffle, a blower tube, or the like is varied, and thus the resultant force exerted on a sheet to be fed is varied. In a known manner, for adjusting an air flow in a printing machine, which air flow varies a sheet transport, what takes place is a corresponding adjustment of the adjusting angle (cock angle) of a valve (ball cock), and this adjustable operating angle is utilized as a controlling variable.
Unfortunately, such an apparatus and this kind of method are not suited to adjusting the aforementioned air flow in such a way that a controlled, precise exertion of force on a sheet to to be transported in the printing machine is obtained by means of the air flow. Because of the resultant fluctuations in pressure in the air flow, even with adjustment of the air flow by means of the prior art devices and methods, it is not possible, or at least is possible only at relatively great effort, to assure adequately stable sheet travel in the printing machine.
It is accordingly an object of the invention to provide an apparatus and method for adjusting an air flow that influences the sheet transport in a printing machine, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and wherein it can be assured that a controlled, precise exertion of force by means of an air flow on a sheet to be transported is attainable in a relatively simple way and replicably, so that stable sheet travel in the printing machine can be assured.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for adjusting an air flow influencing a sheet transport in a printing machine. The apparatus comprises:
an air flow regulating device connected to an air supply device of a printing machine, the air flow regulating device having as a controlled variable an operating parameter of the air flow influencing the sheet transport in the printing machine.
In other words, the objects of the invention are achieved with an apparatus having an air flow regulating device, and wherein an operating parameter of the air flow which varies the sheet transport serves as a controlled variable. This assures the generation of a controlled, precise, replicable exertion of force by means of the air-controlled air flow upon a given sheet to be fed in the printing machine, since all the parameters acting on the air flow in operation in the printing machine, that is, from the air flow generator to the consumer of the air flow, can be compensated for by means of an air flow regulating device of this kind. Such parameters are for instance the ambient pressure, ambient temperature, geometric tolerances, various flow resistances of individual components such as nozzles, valves, and lines, and the like. These parameters that vary the air flow are disadvantageously not detected by means of traditional setting devices and methods, nor can they be compensated for by these methods and devices. By comparison, it is advantageously possible, by means of the apparatus of the invention, to assure a controlled setting of the air flow with compensation for practically all the parameters acting on it, and to assure adequately stable and thus satisfactory sheet travel in the printing machine. Since the apparatus of the invention is not affected by such other operating parameters, and is independent of the printing machine controller, it can be used universally in the printing machine.
Advantageously, the operating parameter is the static air pressure of the air flow, or the air flow rate, or the sheet float height. These operating parameters can be measured continuously, in a comparatively simple, reliable way, and are especially well suited as a controlled variable for operationally optimized setting of the air flow by means of the air flow regulating device. Preferably, the static air pressure is measured in an air exit region, for example at nozzles, or in the interior by blower tubes that are provided. As the operating parameter, the floating height of the sheet (sheet float height), for example above suitable guide baffles, can be used as well.
In accordance with a preferred embodiment of the invention, the air flow regulating device has a regulator, which for performing closed-loop set-point value control is operatively connected to a measuring unit and to a control element, which varies the air flow, forming a closed-loop control circuit. By means of a closed-loop control circuit of this kind, it is comparatively simply possible to achieve effective, reliable setting of the air flow that varies the sheet transport. For performing a set-point value control, only a single suitable, optionally variable set-point value needs to be determined for the operating parameter (static air pressure of the air flow, or air flow rate) used as a controlled variable. Thus the air flow regulating device is independent of the machine controller of the printing machine, making it universally usable throughout the entire printing machine (for instance at a sheet feeder, printing unit, or delivery system).
In accordance with an advantageous feature of the invention, the measuring unit is enabled to ascertain measured values outside the air flow regulating device, downstream of the air supply device and in particular in the immediate vicinity of the sheet transport. As a result, in an especially simple, reliable way, it is assured that controlled, precise exertion of force by the air flow on a sheet to be fed will be attained. The measuring unit (inside the air flow regulating device) and the measured value detection (outside the air flow regulating device) are thus, in this embodiment, spatially separated from one another, and the detection of measured values can be done at any arbitrary, especially suitable place (the immediate vicinity of the sheet transport). Such a favorable measurement location can for instance be a chamber below a nozzle, at a sheet guide baffle, or a chamber in a blower tube in a printing machine.
In accordance with a further, alternative embodiment of the invention, the measuring unit is enabled to ascertain measured values inside the air flow regulating device. In this way, the air flow regulating device can be embodied as a compact structural unit, which is also complete with regard to detecting measured values and is thus also especially flexible in use.
Preferably, the regulator is simultaneously operatively connected to further function elements of the printing machine. Such further function elements can for instance be sensors, which measure the applicable air volume flow, the sheet float height established at a given time, or other physical variables that are useful for effective setting of the air flow. In addition, instead of being connected to other function elements, the regulator can also be operatively connected to other closed-loop control circuits, such as a suction regulator or a central machine controller. In this way, an advantageous data exchange can take place between the air flow regulating device of the invention and other function elements of the printing machine, such as closed-loop control circuits.
In accordance with another feature of the invention, the air flow regulating device has a function element interface that is operatively connected to the regulator. By means of a function element interface, operative connections to other sensors and/or closed-loop control circuits of the printing machine can for instance be created in order to establish a data exchange. The data exchange can be advantageous both for operating the air flow regulating device of the invention and for other operatively connected closed-loop control circuits or control units of the printing machine.
In accordance with a further preferred embodiment, the air flow regulating device is embodied as a replaceable module. An air flow regulating device of this kind can be used in the printing machine in an especially easily manipulated, flexible way. The modular design allows rapid integration of possibly variously embodied air flow regulating devices intended for different operating situations. The choice of a suitable air flow regulating device can be based for instance on a certain, preferred measurement range, a given air flow rate, or the applicable component setting speed. A modular design in the form of a compact building block is especially expedient.
With the above and other objects in view there is also provided, in accordance with the invention, a method of adjusting an air flow influencing a sheet transport in a printing machine. The method comprises:
controlling an air supply device in the printing machine, in particular with the above-outlined apparatus; and
effecting set-point value control at the air supply device and selecting as a controlled variable of the set-point value control an operating parameter of the air flow influencing the sheet transport.
In other words, the above objects are achieved with the method for adjusting the air flow wherein a set-point value control is effected by means of an operating parameter of the air flow, which operating parameter varies the sheet transport and serves as a controlled variable. With the method, it is possible to attain the advantages already mentioned in connection with the apparatus of the invention.
Advantageously, as the operating parameter, the static air pressure of the air flow, or the air flow rate, or the sheet float height is used. These operating parameters are especially well suited to reliably, precisely setting the air flow that varies sheet transport. In particular when the static air pressure value is comparatively low, it is advantageous to use the air flow rate as the operating parameter, since from a measurement standpoint that can be detected more precisely in such an operational case.
In accordance with a concomitant feature of the invention, the operating parameter is measured continuously downstream of the air supply device and in particular in the immediate vicinity of the sheet transport. As a result, it is assured in an especially reliable way that all the parameters acting on the air flow can be compensated for during operation of the printing machine.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and an apparatus for adjusting an air flow that varies sheet transport in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.